In mining operations, bolts are often used to support the roof of the mine. In some applications, a pair of spaced apart inclined bar bolts are anchored into the roof of the mine. Each inclined bar bolt is connected to a truss shoe, which is often called a truss bracket. The truss shoes, which also are spaced apart due to their connection to the inclined bar bolts, are joined together by a pair of horizontally extending members which in turn are joined by a coupler. Typically, the horizontal member consists of a pair of generally horizontally threaded rods, with each of the threaded rods being connected to a corresponding one of the truss shoes.
Certain considerations may be faced when installing a mine roof truss. For example, the inclined bar bolts are typically installed using a bolting machine, and the truss shoes typically are already attached to the inclined bar bolts. The installer than installs the horizontal rods and the coupler that extend between the truss shoes. The horizontal rods may be connected to one another using a variety of couplers, such as a spacer tube or a dog bone coupler. One end of each of the threaded rods must be secured to a corresponding one of the truss shoes. After the assembly is complete, the horizontal rods are tensioned using a tensioning machine.
Each truss shoe has a tapered bore or barrel sized to receive an end of one of the horizontal rods, and a set of wedge pieces are placed in the bore on each one of the truss shoes. These wedge pieces grip the horizontal rod such that tension on the pair of horizontal members tends to draw the wedge pieces deeper into the tapered barrel, thus tightening the grip on the horizontal member.
The installer typically must ensure that the wedge pieces in each of the truss shoes are in place and have not been knocked loose or lost during any of the assembly steps. Many times, the wedge pieces must be manually placed in the tapered portion of the bore in the truss shoe. Unfortunately, these loose wedge pieces can easily fall to the ground during installation, where these small wedge pieces may be lost in the darkness of a mine passage. Of course, valuable time and effort may be expended looking for and recovering any missing wedge pieces. Even if the installer has a ready supply of replacement wedges, the installer often must expend extra time and effort inserting new wedges, which must be accomplished in the often cold and/or dark setting of a mine.